Neurophysiology Lect 14

_______: nerve impulses generated from stimuli.
_______: awareness of stimulifrom the senses
_______: the interpretation of sensation into meaningful forms.

• _____ respond to mechanicalenergy (touch, pressure, vibration, stretch, etc.)
• _____ respond to thermal energy(heat or lack thereof)
• _____ respond to chemical stimuli(irritants, substances released by injured tissue)
• _____ a subset of each type of somatosensory receptors; stimulation results in sensation of pain. They are preferentially sensitive to stimuli that damage or threaten to damage tissue.

_______: The perceptual ability to discriminate objects on the basis of touch.
_______: Perception of the positionand movement of the body, limbs, andhead.

Receptors are specialized to tell two things. ____ a stimulus is occuring and whether or not it is ____ ____

____ ____: the area of skin innervated by a single afferent neuron.

______ corpuscles: have large receptive fields. Located deep in the skin. Respond to high level frequency vibration; Rapidly adapt. Have poor spatial acuity.

______’s corpuscles: Located superficially In skin; respond best to low frequency “flutter”, two point touch, Braille reading: Are rapidly adapting and have small receptive fields.

_____ ____: • Located in superficial part of skin and respond to very low frequency pressure changes. Have discriminative touch to stimuli that facilitate the distinguishing of texture, shape, and edges of objects. Slowly adapting and have very small receptivefields

Touch sensitivity of the skin is measured by the ___ ____ ____ test.
____ Skin: we can detect the two points whenthey are as close as 1.6 millimeters apart.
____ Skin: sensitivity is much less and depends on which part of the body is being tested.

_______: The area of skin innervated by axons from cell bodies in a single dorsal root.

Name the two proprioceptive structures associated with voluntary or skeletal muscles–
– respond to change in length andrate of length or stretching
– respond to change in muscletension (contraction or force)

Muscle Spindle: runs in ____ with the muscle fiber. They are embedded withing _____ muscle fiber.

Muscle spindles are specialized muscle cells innervated both by ____ ____(cell bodies in dorsal root ganglia) and ____ ____ (cell bodies in ventral horn).

Spindle muscle cells (Intrafusal cells) are different.
1) nuclei are in ______ (equatorial region) of cell
2) middle region does ____ _____.
3) ends (polar regions) have contractile filaments and _______

____ ____: typically 1 spindle; large and contract rapidly.
____ ____: typically 1 spindle; small and contract slowly
____: typically 5-10 spindles;smallest and contract slowly

_______ MOTOR NEURONS– smaller (1-8 microns axondiameter) than ______ motor neurons;– form up to 30% of all axons in ventral roots; only innervate spindles.
TWO TYPES:
1.
2.

i. ____ ____ motor neurons innervate Dynamic Nuclear Bag fibersi
i. ____ ____ motor neurons innervate Static Nuclear Bag and NuclearChain fibers.

When activate gamma motor neurons, intrafusal cells contract and they get _____, but their middle segment ______.

Dynamic Bag: motor innervate____ ____; Sensory __
Static Bag: motor innervate ____ ____; Sensory ___ ___
Nuclear Chain: motor innervate _____ _____; Sensory ___ ___

How do muscle receptors send info to CNS andhow does the extrafusal muscle contract?
• Sensory neurons wrap around middle ofintrafusal fibers. They fire when the intrafusalfiber is stretched.
• They are tonically active, so that muscle hastone at rest.
• Their firing rate increases when musclestretches
• Causing extrafusal muscles (innervated by alphamotor neurons) to contract in response tostretch.

True or False: The stretch reflex stimulates the muscle spindle but not the golgi tendon organ.
True False

When the musclecontracts, doesn’t themuscle spindle go slack?

The GTO is found in (series or parallel) with the tendon and muscle fiber. j
The GTO encodes muscle ____.

GTO discharge (slowly/intensely) with isometric contractions.
GTO induces a (poly or mono) synaptic reflex.

1 A alpha (proprioceptors)
A beta (mechanoreceptors)
A delta (pain, temperature)
C (temperature, pain, itch)
Number in order of Fastest to Slowest

Somatosensory information iscarried from the body to theCNS by ___ ___ ___.
_______: Refers to loss of incoming sensory input usually due to damage to sensory fibers; also refers to loss of any afferent input to a structure.

• _______– groupings of neurons and axons for transmission of one type ofinformation
• _______– Perception is a function of firing patterns and receptive fields• Intensity coded as frequency• adaptation
• _______– Orderly mapping of the body surface throughout the CNS
• _______– Organization of regions of the body according to the dorsal rootsystem (dermatomes) entering spinal column• Some overlap

• _____ _____ _____: divide into dorsal rootlets before entering spinalcolumn
_____ diameter axons (touch and position) enter more medial than
_____ diameter axons

Three classes of termination in spinal cord:
______ _____: enter gray matter and synapse on interneurons,motor neurons, and neurons that
project to brain
______ _____: carry sensory information
rostrally to the upperspinal cord and to the brain
______ ______: synapse on interneurons located caudal to levelof entry

• The spinal _____ matter consists of laminar sheets of neurons
• Neurons in the dorsal horn are organized in flat sheets called ______ _____ (after the guy who
discovered them)